Fiber orientation verification for a composite article

ABSTRACT

A fiber orientation verification system includes a sensor and an indicator to identify the fiber orientation within each sequentially laid composite material layer. The indicator projects visible indicator lines upon the lay-up surface which are indicative of a desired orientation for the composite material layer. The sensor and the indicator communicate with a computer module which contains a database including a detailed sequence to assure that each layer is proper placed. The operator is thereby provided with an exact location to lay-up each composite material layer and the proper fiber orientation of that layer. Continued verification is thus provided to the operator.

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/201,101, filed May 2, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to fiber reinforced resin matrixcomposites, and more particularly, to a method facilitating themanufacture thereof which assures that each composite layer is properlyoriented.

A rotor blade spar is the foremost structural element of a helicopterrotor blade assembly inasmuch as its primary function is to transfercombined flapwise, edgewise, torsional and centrifugal loads to/from acentral torque drive hub member. The spar typically extends the fulllength of the rotor blade and mounts at its inboard end to a cuffassembly or fitting which facilitates mounting to the hub member. Due tothe extreme operational loading environment of the rotor blade, fiberreinforced resin matrix composite materials, e.g., Kevlar, graphite andfiberglass, have been employed due to their advantageous strength toweight ratio, corrosion resistance, and improved damage tolerance.

To maximize the benefits of composites it is essential that the fiberorientation be optimally tailored to meet the strength and stiffnessrequirements for a particular application. That is, composites can betailored to be anisotropic (capable of carrying load in a particulardirection) rather than quasisotropic (equal strength in all directions);hence, orienting the fibers in the direction of the load will optimallyresult in the most weight efficient structure.

These considerations must be balanced against the cost and complexity ofa particular fabrication technique. One technique for manufacturingcomposite components includes prepreg lay-up of composite materials. Theprepreg lay-up technique employs the use of discrete plies or layers ofpre-impregnated composite fabric, which are hand-stacked and interleavedover a mandrel assembly. The mandrel assembly is placed in a matchedmetal mold and cured in an autoclave oven for application of heat andpressure.

As described above, to assure the desired strength is achieved, thefiber orientation of each discrete laminate must be assured. Thisprocess is extremely time and labor intensive. Because many layers mustbe hand stacked, and each layer must be properly oriented during thehand lay-up process, there is a relatively high probability of operatorerror, e.g., an operator may inadvertently omit a layer in a multi-plylaminate or fail to properly orient one or more layers. The criticalnature of this laborious hand lay-up process is such that a qualityassurance inspector typically observes an operator during the process toassure no errors are made.

Accordingly, it is desirable to provide a method facilitating themanufacture of a composite structure which assures that each compositelayer is properly oriented while minimizing the necessity of additionalquality assurance personnel.

SUMMARY OF THE INVENTION

A fiber orientation verification system according to the presentinvention provides a sensor and an indicator above a lay-up surface suchthat each has a view of the lay-up surface. The sensor is preferably adigital camera to identify the fiber orientation within eachsequentially laid composite material layer. In one embodiment, eachcomposite material layer includes a contrasting strand which is readilyidentifiable. The indicator is preferably a laser projector whichprojects visible indicator lines upon the lay-up surface to indicate adesired orientation for the composite material layer.

The sensor and the indicator communicate with a computer module whichcontains a database including a detailed sequence of composite materiallayers, fiber orientation, indicator display programs, quality assuranceand operator interfaces to assure that each layer is proper placed asdescribed below.

The computer module initially refers to a desired database to obtain asequence of composite material layers and fiber orientation of thedesired composite component to which the system will verify. In responseto the particular database, the computer module communicates with theindicator to project a plurality of visible indicator lines upon thelay-up surface. The indicator also projects an outline of the firstcomposite material layer such that the operator is provided with a guidefor accurate placement. The operator is thereby provided with an exactlocation to lay-up the first composite material layer and the properfiber orientation of that layer. The display also indicates to theoperator which step he is currently performing and confirmation as tothe proper composite material layer type for that step, e.g. fiberglass,Kevlar, carbon fiber, or the like. Continued verification is thuspreferably continually provided to the operator.

Once the operator positions a composite material layer, the computermodule communicates with the sensor to identify the fiber orientation ofthat layer. The CPU compares the sensed fiber orientation to the properorientation contained in the database for that particular step. Once thefiber orientation is determined, the CPU identifies whether the sensedfiber orientation is equivalent to the predetermined fiber orientationfor that particular step. If the operator has properly positioned thecomposite material layer, the CPU moves to the next step (next lay-uplayer) in the database. This process continues until the lay-up iscomplete.

Should, however, the operator fail to properly position or orient acomposite material layer, the CPU will identify the incorrect layer andprovide an alert to the operator. The operator is thereby alerted to theimproper step, provided with the proper indicator lines and outlinewhile being prevented from proceeding to the next layer.

The present invention therefore provides a system and method whichfacilitates the manufacture of a composite structure which assures thateach composite layer is properly oriented while minimizing the necessityof additional quality assurance personnel.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a general perspective view an composite component;

FIG. 2 is a schematic exploded representation of a plurality ofcomposite material layers adjacent a fiber orientation verificationsystem of the present invention;

FIG. 3 is a flow chart illustrating the steps performed by the fiberorientation verification system;

FIG. 4A is a schematic view of one layer of a composite material and theindicators provided by the present invention; and

FIG. 4B is a schematic view of the next layer after the FIG. 4A layer ofa composite material and the indicators provided by the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a partial perspective view of the root and tipsections 12 and 14, respectively, of a helicopter rotor blade assembly16 having an elliptically shaped composite spar 18 disposed between aleading edge sheath assembly 20 and trailing edge pocket assembly 22.The composite spar 18 extends from the root end portion 12 to the tipend portion 14 along a longitudinal axis 23.

For the purposes of discussion the composite spar 18 includes aplurality of composite material layers which are selectively arrangedand material properties selectively chosen to achieve the foregoingobjectives. It should be understood that although a rotor blade spare isillustrated in the disclosed embodiment, other multi-layer compositestructures will also benefit from the present invention.

Referring to FIG. 2, a schematic exploded representation of a pluralityof composite material layers 30 a-30 x are illustrated relative to afiber orientation verification system 32 according to the presentinvention. It should be understood that although only 5 compositematerial layers 30 a-30 x are illustrated in the disclosed embodiment,this is for clarity only and in actuality a many composite materiallayers 30 a-30 x are typically provided to form a single compositecomponent such as the representative composite spar 18.

A lay-up surface 34 such as a mandrel assembly provides a work surfacefor an operator to hand-stack and interleave the composite materiallayers 30 a-30 x. As is known, the lay-up surface is particularlytailored to the finished component and further description of thedetails thereof need not be provided herein.

A sensor 36 and an indicator 38 are arranged adjacent the lay-up surface34. Preferably, a support structure 39 mounts the sensor 36 andindicator 38 above the lay-up surface 34 so that each have a view V ofthe lay-up surface 34.

The sensor 36 is preferably, a digital camera, however, other sensors 36such as visible, electromagnetic, X-ray, or the like will benefit fromthe present invention. A still image processor sensor or a motionpicture sensor will also benefit herefrom. The sensor 36 operates toidentify the fiber orientation within each composite material layers 30a-30 x. That is, the sensor 36 provides the necessary resolution toidentify the fibers within each composite material layers 30 a-30 x.

In one embodiment, each composite material layers 30 a-30 x includes acontrasting strand 31 (FIG. 4A) which is readily identifiable withgreater clarity within each composite material layers 30 a-30 x suchthat the fiber orientation is more readily identifiable. The contrastingstrand 31 is preferably visibly identifiable, however, otheridentifiable contrast such as a metal fiber will also benefit from thepresent invention. Additionally, or in the alternative, the contrastingstrand 31 may not be identifiable in the visible spectrum but may beclearly visible in, for example only, the infrared spectrum.

The indicator 38 is preferably, a laser projector. The indicator 38projects a plurality of visible indicator lines L (FIG. 4A) upon thelay-up surface 34. The lines are indicative of a desired orientation forthe next composite material layers 30 a-30 x to be applied by anoperator. It should be understood that other indicators such as anarrow, segmented lines, symbols or the like will also benefit from thepresent invention. The indicator 38 also preferably projects an outlineO of the composite material layers 30 a-30 x such that the operator isprovided with a guide for accurate placement of the composite materiallayers 30 a-30 x. This is particularly advantageous should each layernot be identical in shape.

The sensor 36 and the indicator 38 communicate with a computer module 40which is connected to an Operator Interface Module (“OIM”) 42 includinginput and output devices. The OIM 42 includes a display 44, such as ahigh resolution LCD or flat panel display, and an audio speaker 46. TheOIM 22 also includes input devices 48, preferably a plurality of buttonsand directional keypad, but alternatively including a mouse, keyboard,keypad, remote device or microphone. Alternatively, the display 44 canbe a touch screen display.

The computer module 40 includes a CPU (illustrated schematically at 50)and storage device 52 connected to the CPU 50. The storage device 52 mayinclude a hard drive, CD ROM, DVD, RAM, ROM or other optically readablestorage, magnetic storage or integrated circuit. The storage device 52contains a database (illustrated schematically at 54) including adetailed sequence of composite material layers 30 a-30 x, fiberorientation, indicator display programs, quality assurance and operatorinterface as will be further described below. The software for the CPU42, may also be stored in the storage device 52 or alternatively in ROM,RAM or flash memory.

A method for producing the above mentioned composite spar utilizing thefiber orientation verification system will now be described. However, itshould be realized that the use of a composite spar is for illustrativepurposes only, and that the methodology of the present invention may beapplied to other components.

Referring to FIG. 3, a flow chart illustrating operation of the presentinvention is provided. The instructions for the flow chart arepreferably stored in the database 54 (FIG. 2). The computer module 40initially refers to the desired database to obtain the sequence ofcomposite material layers and fiber orientation of the desired compositecomponent to which the system 32 will verify. An operator may select theproper component or the system 32 may be dedicated to a certaincomponent. In addition, the display 44 preferably confirms the selectedcomponent and provides an overview of the process which the operator isto follow.

In response to the particular database, the computer module 40communicates with the indicator 38 to project a plurality of visibleindicator lines L (FIG. 4A) upon the lay-up surface 34. The indicator 38also projects an outline O of the first composite material layers 30 asuch that the operator is provided with a guide for accurate placementof the first composite material layer 30 a. The operator is therebyprovided with an exact location to lay-up the first composite materiallayer 30 a and the proper fiber orientation of that layer. The display44 also indicates to the operator that he is currently performing thefirst lay-up and provides further confirmation as to the first compositematerial layer 30 a type, e.g. fiberglass, Kevlar, carbon fiber, or thelike. Continued verification is thus preferably continually provided tothe operator.

Once the operator positions the first composite material layer 30 a, thecomputer module communicates with the sensor 36 to identify the fiberorientation of the first composite material layer. In one embodiment,the contrasting strand 31 may be provided such that the fiberorientation is readily identifiable to the sensor 36. In anotherembodiment, a digital photograph of the first composite material layer30 a is provided to the CPU 42 for processing. The CPU 42 compares thesensed fiber orientation to the proper orientation contained in thedatabase for that particular step.

Once the fiber orientation comparison is determined, the CPU42identifies whether the sensed fiber orientation is equivalent to thepredetermined fiber orientation of the particular step. If the operatorproperly positions the first composite material layer 30 a, the CPU 42moves to the next step (next lay-up layer) in the database. The firstimage of the properly located and oriented first composite materiallayer 30 a is also preferably stored in the storage device 42.

The computer module 40 again communicates with the indicator 38 toproject a plurality of visible indicator lines L (FIG. 4B) upon thefirst composite material layer 30 a which are representative of thedesired fiber orientation for the second composite material layer 30 b.The indicator 38 also projects an outline O of the second compositematerial layer 30 b. The display 44 now indicates to the operator thathe is currently performing the second lay-up step and additionalinformation pertinent thereto.

As the operator positions the second composite material layer 30 b, thecomputer module communicates with the sensor 36 to identify the fiberorientation of the second composite material layer 30 b. Again, the CPU42 compares the sensed fiber orientation to the proper predeterminedorientation contained in the database for that particular step.

Additionally, the CPU preferably compares the second image of the secondcomposite material layer 30 b taken by the sensor 36 to the image takenof the properly positioned and oriented first material layer 30 apreviously stored in the storage device 44. The CPU 42 can therebydetermine that the second composite material layer 30 b has been locatedover the first composite material layer 30 b, by the change in theimage. It should be understood that the sensor 36 can take a pluralityof images or maintain continues image coverage of the process and theCPU 42 will preferably identify particular stills to store in thestorage device 42. The stills are preferably stored after apredetermined event, for example after confirmation of properlypositioned and oriented composite material layer.

Composite material plies are typically provided with warp and fill “toe”identifiers to cue an operator. These identifiers are also preferablysensed by the sensor 36 and identified during the image comparison asassurance that the second composite material layer 30 b has been locatedover the first composite material layer 30 a. This may be particularlyappropriate where two identical composite material layers havingidentical fiber orientation are sequentially provided in the lay-up. Theimage comparison will thus identify that the correct number of layershave been provided by such that the proper sequence is maintained by achange in the image.

Once proper orientation and position are confirmed the CPU 42 moves tothe next step (next lay-up layer) in the database. This processcontinues until the lay-up is complete. Should, however, the operatorfail to properly position or orient the composite material layer, theCPU 42 will identify the layer is incorrect and provide an alert to theoperator. Preferably, the alert is provided on the display 44. Thecomputer module 40 will also communicate with the indicator 38 tomaintain the indicator lines L and outline O until the step is properlycompleted. The operator is thereby alerted to the improper step,provided with the proper indicator lines L and outline O while beingprevented from proceeding to the next layer.

Furthermore, it is worth stating that the present invention is clearlynot limited to a microprocessor based control system. The system may beimplemented in a non-microprocessor based electronic system (eitherdigital or analog).

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A fiber orientation verification system formanufacturing a multi-layer composite component comprising: a surfacefor receiving a plurality of composite material layers; an indicator forsequentially displaying a desired orientation of each of said pluralityof composite material layers upon said surface; a sensor for sensing afiber orientation of each of said plurality of composite materiallayers; and a controller in communication with said indicator and saidsensor for comparing said fiber orientation of each of said plurality ofcomposite material layers to a predetermined orientation.
 2. Theverification system as recited in claim 1, wherein said surface includesa mandrel.
 3. The verification system as recited in claim 1, whereinsaid indicator includes a laser.
 4. The verification system as recitedin claim 3, wherein said laser projects a plurality of lines upon saidsurface, said plurality of lines indicative of a desired orientation ofeach of said plurality of composite material layers.
 5. The verificationsystem as recited in claim 1, wherein said sensor includes a digitalcamera.
 6. The verification system as recited in claim 1, furtherincluding an operator interface which alerts an operator to an improperorientation of one of said plurality of composite material layers.
 7. Amethod of verifying a proper orientation of each of a plurality ofcomposite material layers during manufacturing of a multi-layercomposite component comprising the steps of: (1) sensing a fiberorientation of a composite material layer; (2) comparing said sensedfiber orientation of said step (1) with a predetermined fiberorientation; and (3) identifying whether said sensed fiber orientationis equivalent to said predetermined fiber orientation of said step (2).8. A method as recited in claim 7, wherein said step (1) furtherincludes sensing a contrasting strand within the composite materiallayer.
 9. A method as recited in claim 7, wherein said step (1) furtherincludes sensing the fiber orientation within the electromagneticspectrum.
 10. A method as recited in claim 7, wherein said step (1)further includes sensing the fiber orientation within the visible lightspectrum.
 11. A method as recited in claim 7, further including the stepof: displaying a desired fiber orientation for the composite materiallayer.
 12. A method as recited in claim 7, further including the stepof: displaying a desired fiber orientation of the composite materiallayer.
 13. A method as recited in claim 7, further including the stepof: displaying a desired location for the composite material layer upona previous composite material layer.
 14. A method as recited in claim 7,further including the step of: displaying a plurality of laser linesrepresentative of a desired orientation of the composite material layer.15. A method of verifying a proper orientation of each of a plurality ofcomposite material layers during manufacturing of a multi-layercomposite component comprising the steps of: (1) displaying a desiredorientation for a composite material layer; (2) sensing a fiberorientation of the composite material layer; (3) comparing said sensedfiber orientation of said step (2) with a predetermined fiberorientation; and (4) identifying whether said sensed fiber orientationis equivalent to said predetermined fiber orientation of said step (3).16. A method as recited in claim 15, wherein said step (2) furtherincludes sensing a contrasting strand within the composite materiallayer.
 17. A method as recited in claim 15, wherein said step (1)further includes capturing an image of the composite material layer. 18.A method as recited in claim 16, further including the step of:comparing a previously captured image of a composite material layer witha present image of the composite material layer.
 19. A method as recitedin claim 15, further including the step of: displaying a plurality oflaser lines representative of a desired orientation of the compositematerial layer.
 20. A fiber orientation verification system formanufacturing a multi-layer composite component comprising: a surfacefor receiving a plurality of composite material layers; an indicator forsequentially displaying a desired orientation of each of said pluralityof composite material layers upon said surface; a sensor for sensing afiber orientation of each of said plurality of composite materiallayers; a controller for comparing said fiber orientation of each ofsaid plurality of composite material layers to a predeterminedorientation; and an operator interface which alerts an operator to animproper orientation of one of said plurality of composite materiallayers.
 21. A method of verifying a proper orientation of each of aplurality of composite material layers during manufacturing of amulti-layer composite component comprising the steps of: (1) displayinga plurality of laser lines representative of a desired orientation of acomposite material layer; (2) sensing a fiber orientation of a compositematerial layer; (3) comparing said sensed fiber orientation of said step(2) with a predetermined fiber orientation; and (4) identifying whethersaid sensed fiber orientation is equivalent to said predetermined fiberorientation of said step (3).
 22. A method of verifying a properorientation of each of a plurality of plurality of composite materiallayers during manufacturing of a multi-layer composite componentcomprising the steps of: (1) displaying a plurality of laser linesrepresentative of a desired orientation of the composite material layer.(2) sensing a fiber orientation of a composite material layer; (3)comparing said sensed fiber orientation of said step (2) with apredetermined fiber orientation; and (4) identifying whether said sensedfiber orientation is equivalent to said predetermined fiber orientationof said step (3).